1. Field of the Invention
The present invention relates to a fluid dynamic bearing unit and a rotating device.
2. Description of the Related Art
Disk drive devices like hard disk drives have been downsized but increased the capacity, and are loaded in various electronics. In particular, loading of the disk drive devices in portable electronics, such as a laptop computer and a portable music player, is advancing.
A Fluid dynamic bearing is known as a bearing unit for a disk drive device. According to this fluid dynamic bearing, a lubricant is filled in a space between a rotating body and a fixed body, and a non-contact condition between the rotator body and the fixed body is maintained by dynamic pressure produced in the lubricant when the rotator body rotates relative to the fixed body.
Disk drive devices employing the fluid dynamic bearing includes a rotating-shaft type disk drive device having the rotating body including the shaft, and a fixed-shaft type disk drive device having the fixed body including the shaft. For example, JP 2011-2024 A, JP2011-12737 A, JP 2011-47439 A, and U.S. Patent publication No. 2010/277833 A disclose conventional fixed-shaft type disk drive devices.
According to the fixed-shaft type disk drive devices of the above-explained conventional technologies, an air-liquid interface that is a boundary between the lubricant and the ambient air is located in a tapered seal provided in a part of the space between the rotating body and the fixed body. The tapered seal accomplishes a role of suppressing a leakage of the lubricant by a capillary phenomenon, and also serves as a buffer of, when a volume of the space changes due to the uplifting of the rotating body and the temperature change in the component, and when the volume of the lubricant changes due to vaporization or thermal expansion, covering such a change.
Accordingly, if the tapered seal is in a poor shape or has a poor dimensional precision, it becomes difficult to covering such a change.
The present invention has been made in view of the aforementioned circumstances, and it is an object of the present invention to provide a fluid dynamic bearing unit and a rotating device which can suppress a production error of a region where the air-liquid interface of a lubricant should be located.